The present invention relates generally to the field of inserting inert or active implants in humans and other animals.
Application of medicaments to tissue sites over an extended period of time has become possible with the use of timed release implants (TRI) which are inserted subcutaneously and provide release of the medicament included in the implant over a significant period of time. Use of TRIs in the contraceptive field and for administration of insulin and other drugs for control of diabetes and other chronic diseases are becoming conventionally accepted means for medication delivery. Modern genetic engineering is increasingly leading to cures of a variety of diseases by replacement of missing body chemistry. The TRI provides a convenient, medically efficient and cost-effective method of introducing such drugs to a tissue site.
TRIs and similar devices are currently implanted surgically or using insertion devices having large-bore needles through which the encapsulated implant is inserted. Such devices typically require high-cost sterilizable components due to the size of the implants themselves. Use of a large-bore needle of the type necessary to pass an implant can cause serious trauma through coring where the hollow needle actually cuts out a plug of tissue when inserted. In order to prevent coring, the use of a stylette or other means to block the needle bore during insertion is required which adds to the complexity of the insertion device, its associated cost and sterilization requirements. Additionally, a determination of the depth of insertion for the implanting site and accurate placement of the implant are required. Conventional beveled needles, particularly of large bore, have a tendency to slice through tissue at an angle to the needle axis, thereby making control of needle insertion and consequent accuracy of placement of the implant, difficult. Alternatively, placement of implants is accomplished at surgically accessed sites by manipulation with forceps or other common surgical tools. These procedures take considerable time to perform, result in greater trauma to the tissue and require extreme care in avoiding contamination of the implant during extraction from packaging and handling. A determination of the depth of the implant typically requires a special gauge, or is measured by approximating the depth of insertion through measurement of the exposed portion of the needle. Either process is typically time-consuming and subject to error or accidental contamination of the implantation site.
It is therefore desirable that an implant insertion device comprise a disposable portion which maintains the implant in a sterile environment and is itself easy to maintain in a sterile condition prior to use. It is further desirable that the implant insertion device include a symmetrical non-coring piercing device with integrated insertion depth measurement to allow accurate insertion of an implant through an existing orifice, subdurally, subcutaneously or in an intramuscular location as appropriate for the particular implant device.
The present invention provides an apparatus and method for delivering a variety of implants, particularly under non-clinical (and non-sterile) environments, to tissue. Prior art devices, as discussed above, require the user to insert the implant into the insertion device immediately prior to use during a surgical procedure, which often requires considerable training so that a fragile implant is not damaged during placement in the insertion device. Moreover, sterility must be maintained during the handling and placement of the implant. The inventive apparatus and method, in contrast, are simple and safe and can be used by minimally-skilled and minimally-trained users, while maintaining the sterility of the implant.
The method and apparatus of the invention are useful for virtually any type of small implant, as described in more detail below. The implant can be inserted as is known in the art, such as into surgically-accessed vessels or tissue, through any natural body orifice, or by subcutaneous introduction. In the case of subcutaneous implanting, the delivery system can be self-introducing, without any surgical preparation of the introduction site.
The implant is sealed in a sterile cartridge until the moment of release at the target site. An implant can be placed with confidence of sterility, even in non-surgical environments. Because of inherent characteristics of the technology, less invasive implanting procedures are feasible, reducing tissue trauma and infection risk. For subcutaneous implanting procedures, only simple local anesthesia is needed. Further, healthcare workers with minimal training can safely administer subcutaneous implanting under primitive field conditions. The skill level required is comparable to that required for administering hypodermic inoculations.
In one embodiment, the invention is directed to an apparatus for introducing an implant or plurality of implants into tissue, which can be human tissue or tissue of another animal, living or dead. The apparatus comprises a cartridge having proximal and distal ends, inner and outer surfaces, and a central bore extending therethrough having proximal and distal ends. An implant, or plurality of implants, having proximal and distal ends is within the central bore. A piston is provided proximal to the implant and slidably maintained within the bore. During operation, the piston moves distally through the bore and urges the implant(s) distally through the bore. The piston can urge the implant(s) directly, i.e., be in direct contact with an implant, or indirectly, i.e., with an intermediate device positioned between the piston and the implant(s). An openable, an preferably pressure-activated, tip section is provided at the distal end of the cartridge enclosing the distal end of the bore and having inner and outer surfaces. The bore is enclosed such that sterility of the implant(s) within the bore can be maintained until released from the cartridge into tissue.
In a preferred embodiment, the piston of the apparatus is in contact with and maintains a seal with the inner surface of the cartridge. The tip section is segmented or frangible into a plurality of segments under pressure from the distal end of the implant and includes means for inducing stress fracture of the tip to create the plurality of frangible segments. The apparatus further comprises reinforcement means extending from the cartridge body to the segments of the tip section to prevent separation of the segments from the tip section subsequent to fracture.
In another embodiment, the invention is directed to a system for inserting an implant, or plurality of implants, into a tissue site. The system comprises an apparatus as set forth above and an insertion tool for urging the piston distally through the bore. The insertion tool preferably comprises means for fixedly or removably attaching the tool to the cartridge and a plunger or other means for distally moving the piston.
In another embodiment, the invention is directed to a method for introducing an implant, or plurality of implants, into a tissue site. The method comprises providing an apparatus as described above. At least a portion of the tip section is inserted into the tissue. The piston is moved distally through the bore, thereby urging the implant(s) distally through the bore. Pressure is exerted on the tip section with the implant(s) to permit the implant(s) to open the tip section and exit the bore. The pressure can be exerted by the implant(s) directly, i.e., with an implant in direct contact with the inner surface of the tip section, or indirectly, whereby an assist plug or other device is in contact with the inner surface of the tip section and an implant so that distal movement of the implant(s) results in distal movement of the assist plug, urging the assist plug against the tip section.